Water dispensing systems, such as machines that vend purified water in response to coin insertion and consumer operation or selection are well-known, particularly in areas where the local, municipal or rural or well-water supply is hard or distasteful, or where potable water is unavailable. A number of vending machines have been designed over the years to provide purified water. Typically, these machines take water from the local source which is often potable, but distasteful, and further purify it by known methods at the vending site for subsequent dispensing. The impurities removed from the water are often disposed of in an effluent stream to the local waste-water system, or to a local septic system.
For example, U.S. Pat. No. 3,207,282 teaches a liquid vending apparatus with liquid purifying mechanisms which consist of carbon filters and ion exchange resins. This system has part of its mechanism duplicated for the dispensing of one-gallon and five-gallon amounts. Subsequent systems typically use some sort of volume control mechanism, such as a flow meter.
U.S. Pat. No. 3,221,859 discloses a relatively simple apparatus for dispensing deionized water that has a back-up ion exchange tank when the primary ion exchange tank is spent. Like many water dispensing systems, this apparatus uses a purity sensor to detect the purity of the vended water and a relay to prevent water dispensing if the purity level is below an acceptable amount.
Another apparatus for purifying water involving pressure filtration is seen in U.S. Pat. No. 3,856,676. It employs a closed storage tank which receives treated water only, with controls for operation of the pressure filtration at intervals to maintain the water in the storage tank between selected levels, and for periodic flushing of the pressure filtration, the flushing water being discharged to the disposal of the rejected water.
Methods and apparatus utilizing staged reverse osmosis (RO) units for purifying and dispensing water are presented in U.S. Pat. No. 4,160,727. The apparatus of this patent also discusses a sump pan to catch spillage, reservoir overflow and reject (brine) flow from the RO stages, where a sump pump is automatically activated when the water reaches a predetermined level U.S. Pat. No. 4,528,093 also teaches methods and apparatus for purifying and dispensing water using RO units, as well as ultraviolet (UV) sterilizers, and additionally provides mechanisms for adding minerals and electrolytes to the dispensed water at the command of the consumer to enhance its taste or to replenish electrolytes lost by the body.
A water purifying and vending apparatus using a particular design of UV sterilizer is set forth in U.S. Pat. No. 4,623,467. The overall system provides two different water paths, depending on the level of purity required by the consumer. It also includes a purity sensor as a check on dispensed water purity.
Additionally, U.S. Pat. No. 4,801,375 teaches a water vending system having a purity sensor, a RO unit, carbon filters, and a volume controller, among other mechanisms, which are run by a "signalling control means", such as an electronic controller. Water is recycled through the RO unit in an attempt to enhance purity. The vending system comprises control mechanisms for automatically dumping the filtered water stored in the tank in the system if there has not been at least a predetermined number of vends of water within a predetermined period of time. Further, contamination of the filtered water in the storage tank by breather air is prevented by UV sterilization of the air continuously before it enters the tank.
A chronological review of this technology will indicate that water dispensing or vending systems have become more complicated over time. To some extent, this increased complexity has been advantageous in that more safeguards and controls may be built into the apparatus, such as by the use of compact electronics. On the other hand, sometimes the increased complexity also contributes to greater likelihood of system breakdown, which is to be avoided.
In other cases, the new features may, in fact, introduce more problems than those solved. For example, in the system of U.S. Pat. No. 4,801,375, the tank contents are dumped if there have not been a predetermined number of vends within a given period of time. It is appreciated that this dumping technique will reduce the chance for bacteria growth within the tank during long periods between vends. However, such as system is potentially wasteful in that in some areas, or during some times, dumping may occur relatively frequently. Such a feature would be particularly disadvantageous if such a machine were in an area where good water is in short supply under the best of circumstances, such as remote arid, desert or semi-desert locales. Additionally, such a system is wasteful of water having value added to it, in the sense that it is already purified to at least some extent.
Thus, it would be advantageous if a water dispensing system could be developed which would avoid some of the problems enumerated above for prior systems, but which would be relatively simple, while providing all of the conveniences expected by the consumer.